Reproducer for sound films



p 1932 E. GERLACH 1,877,844

REPRODUCER FOR SOUND FILMS Original Filed Oct. 19. 1927 I Fig. 2

I Patented Sept. 20, 1932" UNITED STATES PATENT OFFICE ERWIN GIElRLACH, OF BERLIN-SIEMENSSTADT, GERMANY, ASSIGNOR TO SIEMENS & HALSKE. AKTIENGESELLSGHLAFT, OF SIEMENSSTADT, NEAR BERLIN, GERMAN Y, A

CORPORATION or GERMANY,

REPBODUCER FOR SOUND FILMS original application filed October 19, 1927, Serial No. 227,201, and in Germany 'April 9, 1927. Divided and this application filed December 31, 1931. Serial No. 584,079.

My present application is a division of my earlier application filed in the United States Patent Oflice on October 19, 1927, Serial No. 227,201.

In sound films of the type in which the sound record is formed by the boundary between a darkened (exposed) and a light (unexposed) portion of the film, there are frequently spots or other defects on the unl0 exposed portion, and these cause undesirable rustling noises during reproduction, thereby disturbing the true sounds of thepicture, particularly at-points where such sounds are soft. I:

The object of my present invention is to overcome the drawback above referred to. For this purpose, during reproduction of the film, I cover the unexposed portion of the part of the film carrying the sound record, exactly or approximately up to a line connecting the main crests or general apices of the sound-record curve. I prefer to accomplish this by means of a special diaphragm covering the film in the manner just explained. Such diaphragm may be actuated by hand, or it may be controlled by the sound record itself; the latter is the preferred construction. The automatic control may be effected by providing an auxiliary source of light and an auxiliary photo-electric cell associated therewith, which cell receives from said source an amount oflight governed by the traveling sound record. In circuit with this auxiliary cell I arrange one or more choke coils and, in certain cases, condensers in parallel therewith, so that the diaphragm will be controlled only in response to the fluctua tions in the mean value of the photo-electric 40 cell current corresponding to the sound record. 7

Reference is tobe had to the accompanyingv drawing, in which Figs. 1 and 2 are diagrammatic views showing two embodiments of my.

invention.

- The reproducing apparatus illustrated comprises a source of light Z, an optical sys tem indicated by the two lenses, and a photoelectric cell z, with the circuit of which the reproducing loud speaker is connected directly or indirectly. The beam of light proceeding from the source Z is controlled by the sound film 0, the fluctuations of lightproducing, in the well-known manner, corresponding fluctuations of current in the photoelectric cell z, which current fluctuations in turn are converted into sound fluctuations in the loud speaker a. The reproducing apparatus includes a diaphragm or shutter consisting of a stationary member m and a movable member n. By means of a lever g fulcrumed at g, the movable shutter member n is connected with the armature of an electromagnet 1' energized by the current of an auxiliary'system. This system comprises an auxiliary source of light t, a second optical or lenssystem, and a second photo-electric cell 1). The sound film 0 (that is, the sound vrecord on said fihn) controls the beam of light proceeding from the auxiliary source t, in the same manner that it controls the beam of light proceeding from the source of light Z in the 7 main system.

The currents of the photo-electric cell 1) are made to energize the electromagnet r, an amplifier (not shown) being preferably interposed between the cell p and said electromagnet. Whenever the armature of the magnet 1' moves, the lever q will cause the shutter member n to be shifted, the construc tion and arrangement of the members m, n being such that the shifting of the movable member 1% will alter the width (transversely of the film) of that portion of the beam of light proceeding from the source l which the shutter m, 'n permits to reach the film at that particular moment. For instance, as shown in-Fig. 2, the member m may have a horizontal upper edge, and the member n an inclined lower edge, it being obvious that acleft, will cording as the member n is raised or lowered, the horizontal dimension or width of the wedge-sha ed slit or'openin shown at the e increased or ecreased. The efiective width of the beam of light is thus varied, the control being efiected in such a manner that the shutter will exclude light from the transparent portion of the film exactly or approximately to a line connecting the general apices of the sound-record curve. The extent to which the shuttering action is carried, and therefore the extent to which the shutter member n moves, are governed by the amplitude of the same sound record which modulates the current in the photoelectric cell p. i I

In order that the shutter member n controlled by the electromagnet 1' may be shifted only in accordance with the shape of said line connecting the general apices of the sound-record curve, and may not be shifted in the rhythm of the sound fluctuations themselves, I prefer to provide, in the circuit connecting the photo-electric cell ;0 and the electromagnet r, one or more choke coils v and condensers u. Such a unit '0, u constitutes a filter chain preventing the electromagnet 'r from being affected by currents corresponding to. relatively rapid sound vibrations. The filter chain however does not interfere with the control of the electromagnet by currents of relatively low frequency corresponding to slow variations in the intensity of the sound.

Instead of providing choke coils in the circuit as referred to above, I may obtain the same result by giving the beam of light proceeding from the source 6 such a width, at the point of its passage through the film 0, that it will be a multipl of the width of a single wave of the lowest sound frequency recorded. In this case also, only the mean amplitude of the sound record curve will influence the shutter m, n, the latter not being afi'ected by the individual waves or vibrations. The distance between the main optical system 1, m, n, stand the auxiliary system 1), t

is so selected that the time which the film 0 takes to travel this distance will be equal to the reaction time of the auxiliary system from the moment of the modulation of the beam of light proceeding from the source If, to the moment when the shutter member n moves. In the main, this reaction time derise of the current, and the winding 0 the electromagnets 'r.

The form of shutter shown in Fig. 2, while known in connection with other devices, is novel in the particular relation in which I employ it, and is of special advantage in connection with my present invention. The two co-operating edges of the shutter members m, a, form an acute angle with each other, and thus any n or down movement of the member n (as in icated by the arrow) will eflI'ect a change in the width of the covered or overlapping portions of these members m, n, than the extent of such vertical movement.

Various modifications may be made without departing from the nature of my invention as set forth in the appended claims.

I claim:

1. In an apparatus for reproducing sound by means of sound films in which the width of the darkened film portion varies according to the sounds, means for projecting a beam of light on the film, a shutter located in the path of said beam and variable erpendicularly to the path of the film, and means for controlling said shutter in such a way that the film portions extraneous to the sound record will be shuttered substantially to a line connecting the general apices ,of the sound record curve.

2. In an apparatus for reproducing sound by means of sound films in which the width of the darkened film portion varies according to the sounds, means for projecting a beam of light on the film, a shutter located in the path of said beam and variable perpendicularly to the path of the film, and an auxiliary photoelectric system controlling said shutter in such a way that the film portions extraneous to the sound record will be shuttered substantially to a line connecting the general apices of the sound record curve.

3. In an apparatus forreproducing sound by means of sound films in which the width of the darkened film portion varies according to the sounds, means for projectin a beam of light on the film, a shutter located in the path of said beam and variable perpendicularly to the path of the film, and an auxiL' iary' photo-electric system controlling said shutter electromagnetically in such a way that the film portions extraneous to the sound record will be shuttered substantially to a line connecting the general apices of the sound record curve.

4. In an apparatus for reproducing sound by means of-sound films in which the width of the darkened film portion varies according to the sounds, means for projecting a beam of light on the film, a shutter located in the path of said beam and variable perpendicularly to the path of the film, and an auxiliary photoelectric system comprising a source of light and a light sensitive cell, said auxiliary system controlling said shutter in such a way that the film portions extraneous to the sound record will be shuttered substantially to a line connecting the general apices of the sound record curve.

5. In an apparatus for reproducing sound by means of sound films in which the width of the darkened film portion varies according to the sounds, means for proj'ectin'g'a beam Y in the path of light on the film, a shutter located in the path ofisaid beam and variable perpendicularly to the path of the film, and an auxiliary photo-electrlc system comprising a source of light, a light sensitive cell, an electromagnet controlled by said cell, a choke and a capacity in circuit with said electromagnet and said cell, and means, controlledby said electromagnet, for controlling said shutter in such a way that the film portions extraneous to the sound record will be shuttered substantially to a line connecting the general apices of the sound record curve.

6. In an apparatus for reproducing sound by means of sound films in which the width of the darkened film portion varies according to the sounds, beam of light on the film, a shutter located of said beam and variable erpendicularly to. the path of the film, an an auxiliary photo-electric system comprising a source of light, means for projecting a beam of light from said source on the film and giving such beam, at its point of passage through the film, a width which is a multiple of the width of a single wave of the lowest sound frequency recorded, a light- I sensitive cell in the path of said beam, and

- means, controlled by said cell, for controlling said shutter in such a way that the film portions extraneous to the sound record will be shuttered substantially to a line connecting means for projecting a distance between the points atwhich the two beams of light strike the film being such that the time consumed by the film in traveling this distance will be equal to the reaction time. of the auxiliary system ,from the moment of the modulation of the auxiliary beam of light to the moment of the movement of theshutter located in the path of the main beam of light.

In testimony whereof I affix'my signature.

- ERWIN GERLAGH.

p the general apices of the sound record curve.

7. In an apparatus for reproducing sound by means of sound films in which the width of the darkened film'portion varies accord-- ing to the sound, means for projecting a beam of light on the film, a shutter located I in the path of said beam and variable perpendicularly to the path of the film, said shutter com rising a stationary member,

and a mova le member the co-operating edges of which form an acute angle with one another and are adapted to overlap more or less, and means for controlling the movable member of said shutter in such a way that the'film portions extraneous (to the sound record will be shuttered substantially to a line connecting the general apices of the sound record curve.

' 8. In an apparatus for reproducing sound by means of sound films in which the width of the darkened film portion varies according to the sounds, means for projecting a beam of light on the film, a shutter located in the path of said beam and variable perpendicularly to the path of the film, and an auxiliary'photo-electric system comprising means for projecting a beam of light on the film at a point different from the firstmentioned beam, and controlling said shutter in such a way that the film portions extraneous to the sound. record will be shuttered substantially to a line connectin the general apices of the sound record curv the. 

